Clutch Rubbers

It must be worth a try.  The first ones I fitted (about 20 years ago) went in without too much of a struggle.  The last ones (about 6 years ago) were impossible and I trimmed them with Stanley knife.  Even Les at Russell Motors couldn't get them in.
Perhaps you have ones from the same bad batch.  Or are they all like this?

Has anyone been brave enough to slather the gaps with grease (debonding) and fill with silicone sealant?!!

Hi Philip, if it reassures you I had exactly the same problem when I replaced my Navigator clutch rubbers.   Despite ordering the correct part number from NOC spares and making a special tool so I could compress the first side I couldn't get close to fitting the second side.   In the end I too had to resort to the Stanley knife.  After several days of battle, lots of blades and sore fingers I got it back together again.  Happily it has run without problems for over 4000 miles since completion so the approach does work!
Nick

i used a belt sander to shave a sliver off both edges . it works a treat

,

Submitted by Ron Tomkins on Fri, 29/11/2019

Installing new cush rubbers

after many hours of trying to install cush rubbers by holdingthe back plate still and rotating the clutch body with a variety of levers, jerry built extended strap levers and even ratchet straps, an alternative procedure occurred to me. I placed all three large inserts into their positions in the spider and compressed them by inserting a short steel wedge into one of the empty small compartments. Relatively gentle tapping on the wedge rotates the spider, resulting in high compression of the large rubbers. Two of the smaller rubbers can then be inserted. With five of the  six inserts in position the wedge can be removed without resulting in too much rotation of the spider such that the last small insert goes in with minimal persuasion. 

I feel certain that I will be accused of something involving grandmothers and eggs but I am hoping that by airing this method it might help those who might be frustrated with other procedures.

I would be wary of reducing the size of the rubbers to get them to fit.  They need to be a very tight so they are properly supported.  If not, the shock absorber will not function as intended and the life of the rubbers will be significantly reduced.

Special tools are needed to do the job properly. 

The last rubbers I fitted were in a Triumph clutch.  I welded the clutch end of a worn out gearbox main shaft to the mid-point of length of steel bar some 4ft long,  Then clamped the clutch centre on to a substantial bench.
The reason for attaching the splined shaft to the centre of the bar was so that a pure torque could be applied rather than a less controlled leverage if it were at the end of the bar.

Took a lot of force to twist the spider to make space for the rubbers. Plenty of rubber lube helped. A two man job, one to twist, one to work the rubbers in. 

I firmly believe that time should be given to making or procuring the right tool for the job.  In this case it makes what might seem a near impossible job doable.   I may be making one for the Navigator clutch as  I want to modify it.  I've accumulated the necessary bits for the job, the rubbers need replacing.

Incidentally, the Triumph factory did the job the opposite way to my way.   The spider was placed over a main shaft clamped to a bench.  An internally splined sleeve with two substantial handle slipped over the clutch centre and twisted to fit the rubbers. 

Les at Russell Motors had "the right tool". And so do I.  Again...I don't know what the new ones are like, but the ones I bought several years ago simply would not fit.  They were too large as well as too hard.  When they were jammed in, the sides overflowed and the cover could not be fitted.

Norvil list six different rubber inserts. 

A large and a small for three different clutch variations. 

Suggest owners get the correct parts book for their Norton and armed with the correct part numbers, see if the Norvil part numbers match. 

I made a mainshaft spline form that I could hold in a strong vice. Spline vertical, spider on shaft. Insert larger rubbers into clutch centre. Clutch holding tool with long handle to twist centre and compress large rubbers. Insert small rubbers. 

Like John Crocker above and per Norton Twins Manual. 

Peter

If the rubbers are to spec, that is to say the right size, right shape and the material is the right specification, then everything should fit using the right tools for the job. 
There should be absolutely no need to trim the rubbers to make them fit.

After reading Peters post I looked at the offerings of several spares suppliers.  Photo attached of the results. ( Hopefully self explanatory.  The " D L S" copies Norvils shorthand for Dominator, Lightweight, Single.  L and S before part number, large and small rubbers).

From this, it looks like that the later models (different gearbox) used the same rubbers as the heavyweights.  Whereas the earlier models used a different set of rubbers.
Could this be the cause of the fitting problems?  I've been unable to find pictures of the earlier lightweight rubbers to compare with the later/heavyweight rubbers. 

If they have gone hard due to age seal them in a ziplock bag with some coconut oil. Check their plasticity as time passes. If it's a modern silicon rubber soak in silicon grease diluted with WD40.

A quick softening can be achieved by having the rubbers in hot soapy water. as you install them in the normal way. 
j

The ones I bought for my Dominator a while ago were far too large and hard to fit. Too wide also.
There was no hope of compressing them.
I had to cut them away - more than trimming them - extensively.
They were more like plastic than rubber.